Doha - Double Olympic champion Caster Semenya won her last 800 metres race on Friday before the introduction of controversial rules limiting testosterone levels in female athletes which she had battled for years to stop.

The South African was running at the Diamond League meeting in Doha two days after the Court of Arbitration for Sport (CAS) rejected her appeal to get the governing body's (International Association of Athletics Federations) new regulations thrown out.

She must now begin taking medication to lower her testosterone levels if she wishes to compete over that distance based on the new rules, which CAS said on Wednesday were necessary to ensure fair competition.

Under the rules to take effect on May 8, female athletes with high natural levels of testosterone wishing to compete in events from 400 metres to a mile must medically limit that level to under 5 nmol/L, which is double the normal female range of below 2 nmol/L.

Testosterone is a hormone that increases muscle mass, strength and haemoglobin - which affects endurance.